JP2000093440A - Implantable prosthesis with bone engaging rib - Google Patents

Abstract

(57) Abstract: An implantable prosthesis component is provided. The prosthesis component includes a femoral stem and a plurality of bone engaging ribs.
2e. The plurality of ribs are shaped so that they can engage with dense reticulated bone during implantation. In addition, these ribs are shaped and spaced to engage the bone of the predetermined dense network to achieve optimal fixation within the medullary canal of the femur.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a joint prosthesis, and more particularly, to a joint prosthesis that can be inserted into the medullary canal of a bone.

[0002]

[0002] Arthroplasty is a known surgical procedure in which a diseased and / or damaged natural joint is replaced by a prosthetic joint. Arthroplasty is generally performed at joints such as hips, knees, and elbows. Conditions such as the health of the natural joint to be replaced determine the type of prosthesis required for implantation. Hip arthroplasty is a surgical procedure in which the natural femur is excised and the femoral component is implanted into the medullary canal. In total hip arthroplasty, the natural acetabulum is replaced by an acetabulum component, which provides an articular surface to the head of the femoral component.

[0003] Effective implantation of a femoral component requires proper initial fixation and long-term stability of the prosthetic component. One example of a technique for securing the femoral component within the medullary canal is the use of bone cement. However, known bone cement materials are known to have some deficiencies. For example, the implanted prosthesis may loosen over time, ultimately requiring surgical revision of the implant.

[0004] Another attempt to enhance the effectiveness of securing the press-fit prosthetic component within the medullary canal involves the use of various surface features formed on the implant, such as unevenly spaced steps. Although such features have a specific fixation effect on bone, it is difficult to optimize the overall shape of the prosthesis implant for an effective and dense cancellous bone. For example, it is known that the densest reticulated bone at the proximal end of the femur is generally located on the anterior and posterior sides of the femur. However, implants with evenly spaced ribs do not take into account the bone density gradient in the reticulated bone, making it difficult to optimize the initial implant fixation.
Initial implant fixation is important to minimize movement between the bone and the implant, which increases the likelihood of long-term implant fixation as bone grows on the surface of the implant .

[0005] In addition, the external shape of some femoral components needs to be removed in order to fit high quality dense reticulated bone into the implant. This can also occur with features that are implanted in a bone of a less dense network than the bone to be removed. In addition, some implants are shaped to conform to cortical bone, so that any surface features are placed regardless of the density of the reticulated bone.

[0006]

Therefore, a surface profile in the form of a bone engaging rib having a shape for optimal fixation of the dense network into the bone when implanted into the medullary canal of the bone. It is desired to provide a prosthetic component having a section.

[0007]

SUMMARY OF THE INVENTION The present invention provides a joint prosthesis having an overall profile and surface shape that optimizes fixation characteristics. It should be noted that while the present invention is primarily illustrated and described as a femoral component of a hip prosthesis, the present invention provides a knee,
It is understood that other joint prostheses such as elbows are also applicable.

In one embodiment, an artificial hip femoral component for implantation into the medullary canal of a femur comprises a plurality of longitudinal bone engaging ribs formed anteriorly and posteriorly of the femoral stem. ing. The ribs are sized and spaced for optimal fixation in a bone of a predetermined density of the network. It should be noted that the desired shape, spacing and number of ribs can be determined by various factors such as the density profile of the reticulated bone and the size of the implant.
In one embodiment, at least three longitudinal ribs are formed on the surface of the stem, and the spacing between these adjacent ribs increases in one direction. These ribs ensure initial implant fixation, minimize micromotion of the implant, and facilitate load transfer from the implant to the bone.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully understood from the following detailed description, taken in conjunction with the accompanying drawings, in which: FIG. The drawings described below illustrate the concepts disclosed in the present specification and should be understood to facilitate understanding of the present invention. Moreover, the drawings need not be specifically dimensioned, and the scope of the present invention is not limited by the relative dimensions of the various components in the embodiments shown and described herein.

FIG. 1 illustrates an exemplary embodiment of a hip prosthetic femoral component or stem 10 having a plurality of bone engaging ribs 12. This femoral component 10
Is suitable for implantation into the medullary canal of the patient's femur. As described below, the ribs 12 are spaced and dimensioned to optimize fixation in the dense network of bone in the medullary canal of the femur. The overall shape of the femoral component 10 optimizes the contact between the ribs 12 in place and the bone of the dense network.

As used herein, the term “medi (medi)
al) "," lateral "," anterior "
And the relative position and orientation of the "posterior" are relative to the human body. Further, when used in combination with a hip prosthetic femoral component, these terms generally refer to the orientation of the component after implantation in a patient. However, these terms are relative and may be different for prosthetic components other than the hip prosthetic femoral components described herein.

The femoral component 10 has an upper or proximal portion 14 and a lower or distal portion 16.
A first plane 18 (see FIG. 1) divides the femoral component 10 into a center (central side) 20 and a side (side) 22 and a second plane 24 (see FIGS. 2 and 3). 3) divides the stem 10 into a front portion (front side) 26 and a rear portion (rear side) 28.

A neck 30 extends from the proximal end 14 of the femoral component 10 and is configured to engage a head or ball joint (not shown). The head joint joins into the natural acetabular cavity or prosthetic acetabular component.

The ribs 12 are provided on both the anterior portion 26 and the posterior portion 28 of the stem 10 by the femoral component 10.
Are shown generally located at the proximal end 14 of the nosepiece. However, the ribs 12 have a front portion 26 and a rear portion 28.
Can be formed in either or both. Further, it can be seen that these ribs 12 can be formed on the central portion 20 and / or the lateral portions 22 of the femoral component 10. In addition, one or more ribs 12 can extend over substantially the entire length of the stem or a relatively short distance.

In general, the ribs 12 need to extend longitudinally over the surface of the femoral component 10 to correspond to the location of the densest bone in the medullary canal in the femur. The location of the finest reticulated bone in the patient's femur can be determined with the aid of computed tomography (CT) or other systems known to those of ordinary skill in the art. Such information can be used to tailor a specialized prosthesis for any patient.

Thus, the shape and spacing of the ribs 12 can be varied to optimize the fixation of the dense network within the bone, permitting effective load transfer to the bone, and furthermore, the bone of the implanted part. To minimize the small movement of The rib 12
With the bone-engaging edge 13, it can have a variety of cross-sectional shapes, including triangles, quadrilaterals and general convex shapes. In addition, adjacent ribs can be substantially parallel and can be oriented to form a slight, ie, less than, 10 ° angle. The end 13 may be continuous or formed by separate parts. In addition, the end 13 can be a constant height, or can be a constant pattern or irregularly tapered or wavy. The term edge, as used herein, includes a single peak and multiple peaks. In the embodiments shown in FIGS. 1 to 8, in particular in FIGS. 4 to 6, the ribs 12 have a triangular cross section, the height of the ends being reduced towards the distal end.

As shown in FIG. 8, each rib 12 has a central side 34 and a lateral side 36 that intersect to form an end or top 13 and that adjacent ribs 12 are separated by grooves 38. The ends 13 of the ribs 12 are effective to engage the dense reticulated bone to secure the femoral component within the medullary canal. In addition,
It can be seen that the central side 34, side 36 or groove 38 can be textured to promote bone ingrowth.

Those skilled in the art will appreciate that the ribs 12 are determined by various parameters. For example, the angle A formed by the central side 34 and the lateral side 36 can vary from about 5 ° to about 90 °. This angle A can be optimized to minimize movement between the implant and the bone. In one example of the embodiment, angle A is about 60 degrees.

The height H of the ribs 12 can range from about 1 millimeter to about 6 millimeters. This height can be optimized to minimize migration of the implant without penetrating into cortical bone. In one embodiment, the height H of the ribs 12 can be varied along the length of the stem 10 to achieve the best fixation or contact with dense reticulated bone. Further, the height (H) can be varied between adjacent ribs. 1 to 8
In the embodiment shown in FIG. 5, the height H is maximum near the proximal end 14a of the stem 10 and gradually decreases in the distal direction.

Also, the spacing and number of ribs 12 formed on stem 10 can be varied to optimize the fixation of the dense network in bone. The term “spacing” as used herein refers to the distance between the ends 13 of adjacent ribs 12. In one example of the embodiment,
The interval between the ribs 12 increases toward the center. That is, the interval SM between the center rib 12a and the center rib 12b is larger than the interval SL between the side rib 12d and the side rib 12e (see FIG. 7). In the illustrated embodiment, the spacing between these ribs 12 can vary from about 2 millimeters to about 7 millimeters.

The number of ribs 12 formed on the stem surface is
It can be varied by a number of factors, such as bone density, implant size and rib pitch. This rib 1
The number of two can vary from three ribs to about seven ribs for relatively large femurs. In the embodiment shown in FIGS. 1 to 8, the femoral component 10 has five ribs 12a.
Or ribs 12e.

Further, the length of the rib 12 can be changed. In one example of the embodiment shown in FIGS.
A plurality of ribs 12a to 12e are formed on each of a front portion 26 and a rear portion 28 of the stem 10.
The three intermediate ribs 12b to 12d are the stem 10
From the base end 14a of the stem 10 to the vicinity of the intermediate portion 15 of the stem 10, and the most central rib 12a and the most lateral rib 12e extend at a shorter distance than the intermediate ribs 12b to 12d. ing. That is, the most central rib 12a (see FIG. 7) extends from the base end 14a to a point about one-fourth of the entire stem length.
e extends for about one third of the total stem length. This length should be optimized to minimize the possibility of cracking of the femur and maximize the transfer of torsional load from the stem to the bone if the stem sinks or falls.

It should be noted that the ribs 12 formed on the front portion 26 of the stem 10 can be substantially symmetric with respect to the ribs 12 formed on the rear portion 28, and that they can be made asymmetric. Think you can understand. This asymmetric anterior / posterior rib spacing is suitable for optimizing fixation properties at different bone densities. That is, the ribs formed in the anterior portion 26 can be optimized for anterior reticulated bone having a first density and the ribs formed in the posterior portion 28 can be optimized for a posterior reticulated bone having a second density. Can be optimized for. In the embodiments of FIGS. 1 to 8, the front ribs and the rear ribs are generally symmetric.

Prior to implanting the femoral stem into the patient's medullary canal, the patient's femur is examined with a CT scanning system to confirm the density profile of the reticulated bone. For example, bone density can be determined proximal to one third of the femur in a 2 millimeter frame. The outer contour and rib shape of the femoral component 10 facilitates positioning of the bone engaging ribs 12 within the bone of a given network. Further, by implanting the femoral component 10 and ribs 12 into a dense network of bone, optimal initial fixation, favorable load transfer to the bone, and minimal micromotion are achieved. Optimal rib geometry also minimizes micromotion at the interface between the bone and the implant when an axial or torsional load is applied. It should be noted that this micromotion must be less than about 50 microinch to promote bone ingrowth.

In another embodiment, the prosthetic component system includes a plurality of components, such as a femoral stem, each component having a particular profile and rib shape. The shape of the femoral component can be formed based on information about bone density accumulated by many patient profiles. With this information, implants of various sizes can be formed, and the choice of one of these implants can provide optimal fixation properties for most patients. Therefore, after performing the CT scanning process to obtain the bone density profile of the patient, appropriate components are selected based on the bone density information and the bone dimensions. The femur is adjusted to receive the selected femoral stem so that the stem can be implanted into a bone of a predetermined density of the network to achieve optimal fixation properties.

In one example of the particular embodiment shown in FIGS. 1-8, the femoral component 10 is formed with five ribs 12a-12e. The overall dimensions of stem 10 include a length of about 170 millimeters without neck. Also, the width W of the stem 10 (central direction-side direction,
6) and the depth D (forward-backward) increase from the distal end of the stem 10 to the proximal end 14a thereof. The width W is about 10 mm at the tip, about 16 mm at the cutting line 6-6,
It is about 20 millimeters at section line 5-5 and about 42 millimeters at section line 4-4. On the other hand, the depth D is about 7 millimeters at the tip, about 9 millimeters at the cutting line 6-6, about 11 millimeters at the cutting line 5-5, and about 18 millimeters at the cutting line 4-4.

The five ribs 12 are a middle rib 12b to a middle rib 12d having a length of about 80 millimeters, the most central rib 12a having a length of about 40 millimeters and a
Includes the most lateral rib 12e of millimeter length.
These ribs 12a to 12e extend from the base end 14a of the stem 10.

The ribs 12a to 12e have a width B of about 2.0 millimeters near the cutting line 4-4.
(See FIG. 8). The width B gradually decreases to about 0.5 mm at the cutting line 5-5. In this way, the transfer of the torsional load at the proximal load can be maximized, thereby reducing the possibility of proximal bone resorption and prolonging implant fixation. The likelihood increases.

The distance between adjacent ribs 12 increases toward the center, and when measured from end to end, the distance between adjacent ribs is about 5.1 mm (12a, 12a).
b), about 4.8 mm (12b, 12c), about 4.3 mm (12c, 12d) and about 3.8
Millimeters (12d, 12e). Also, rib 1
2 has a height H of about 1.7 millimeters.

[0030] Those skilled in the art will be able to ascertain further features and advantages of the invention based on the above-described embodiments. Therefore, the present invention
It is to be understood that the scope is not to be limited by what has been particularly shown and described, except as to the appended claims and the embodiments described below. It should be noted that the entire contents of all publications and documents cited in this specification are included in this specification as references.

Specific embodiments of the present invention are as follows. The prosthesis component according to claim 1, wherein (1) the first rib and the second rib are parallel to each other. 2. The prosthesis component of claim 1, wherein the first and second ribs have different lengths. (3) The prosthetic component of claim 1, wherein the prosthetic component is a femoral component of a crotch prosthesis. (4) The prosthetic component according to embodiment (3), wherein the second rib is lateral to the first rib. The prosthesis component according to claim 1, wherein the first and second intervals vary from about 4 millimeters to about 6 millimeters.

(6) The prosthetic component of claim 1, wherein each of the plurality of ribs has a bone engaging end formed by a top of the rib. 7. The prosthetic component of claim 6, wherein the bone engaging end has an increasing height along the length of the prosthetic component. (8) The prosthetic component according to embodiment (7), wherein the height decreases from a proximal end to a distal end of the prosthetic component. 9. The prosthesis component according to claim 1, wherein the plurality of ribs each have a height in a range from about 0.5 millimeters to about 5.0 millimeters. (10) The prosthesis component according to claim 1, wherein the first rib has a height different from a height of the second rib.

(11) The prosthetic component according to claim 1, wherein each of the plurality of ribs has a substantially triangular cross section. (12) The plurality of ribs further include a fourth rib and a fifth rib.
A first rib, a second rib, a third rib,
The prosthetic component according to claim 9, wherein at least one of the fourth and fifth ribs extends from one end of the body to a point about one-half of the length of the body. . (13) The prosthetic component according to claim 1, wherein the prosthetic component is a femoral component of a crotch prosthesis, and the rib is formed in a front portion of the main body. (14) The prosthetic component according to the mode (13), wherein a rib is further formed on a rear portion of the main body. (15) Further, a second portion formed on the rear side of the stem.
3. The femoral stem component according to claim 2, comprising a plurality of ribs, the second plurality of ribs extending substantially parallel to a longitudinal axis of the stem.

(16) The femoral stem component according to embodiment (15), wherein adjacent ribs of the second plurality of ribs have an increasing interval in a central direction. (17) The femoral stem component according to embodiment (15), wherein the first plurality of ribs and the second plurality of ribs are generally symmetric. (18) The femoral stem component according to embodiment (15), wherein the first plurality of ribs and the second plurality of ribs are generally asymmetric.

[0035]

As described above, according to the present invention,
A prosthetic component having a surface feature in the form of a bone engaging rib with a shape for optimal fixation of the dense network into bone when implanted in the medullary canal can be provided.

[Brief description of the drawings]

FIG. 1 is a front view of a hip prosthetic femoral component in accordance with the present invention.

2 is a side view of the femoral component of FIG. 1 on the lateral side.

FIG. 3 is a side view of the central part of the femoral component shown in FIG. 1;

FIG. 4 is a cross-sectional view of the femoral component of FIG. 1 taken along line 4-4.

FIG. 5 is a cross-sectional view of the femoral component of FIG. 1 taken along line 5-5.

FIG. 6 is a cross-sectional view of the femoral component of FIG. 1 taken along line 6-6.

FIG. 7 is a top view of the femoral component of FIG. 1;

FIG. 8 is a detailed view of a portion of the femoral component of FIG. 7 taken along line 8-8.

[Explanation of symbols]

 10 hip prosthesis femoral component (stem) 12 bone engaging rib

Continued on the front page (72) Inventor Alfred F. Decaro United States, 06903 Connecticut, Stamford, North Meadows Lane 61 (72) Inventor Bruce Cariri United States, 02167 Massachusetts, Chesnut Hill, Hammond Pond Parkway 26

Claims (2)

[Claims] 1. An elongated body having a surface and a longitudinal axis, and a plurality of ribs formed on a surface of the body and extending substantially parallel to the longitudinal axis of the body, wherein the plurality of ribs are provided. A first rib, a second rib adjacent to the first rib, and a third rib adjacent to the second rib, between the first rib and the second rib. The implantable prosthetic component, wherein the first spacing is greater than the second spacing between the second rib and the third rib. 2. A stem having a proximal end and a distal end, a longitudinal axis, and a front side and a rear side, and formed along a length of a front side of the stem substantially parallel to the longitudinal axis of the stem. A prosthetic femoral stem component comprising a first plurality of substantially parallel ribs, wherein the spacing between adjacent ribs in the plurality of ribs increases in a medial direction.